Abstract
The objective of this study was to investigate the effects of drought stress on the activity of antioxidant enzymes and osmotic adjustment substance content in the tillering period of drought-sensitive and drought-tolerant rice cultivars. The results showed that the superoxide dismutase (SOD), peroxidase (POD), catalase activity (CAT), hydrogen peroxide content, soluble protein content and soluble sugar content increased with the accumulation of time and intensity of drought stress. Compared with the drought-sensitive cultivar, drought-resistant cultivar had a smaller photosynthetic affected area, longer CAT enzyme activity duration, and lower H2O2 accumulation. Unlike POD and CAT enzymes, which maintain the ability to scavenge hydrogen peroxide under long drought conditions, ascorbate peroxidase (APX) enzymes seem to be a rapid response mechanism to scavenge hydrogen peroxide under drought stress. Under a −10 kPa water potential, using soluble sugars on the osmotic adjustment ability of the drought-resistant cultivars was more efficient; under −40 kPa water potential, drought-resistant cultivars can maintain relative high levels of ascorbate (ASA) content in the short term. After the restoration of irrigation, the indices gradually returned to control levels. The ASA content showed faster accumulation ability in drought-resistant cultivars and faster recovery. The soluble protein content recovered more slowly in drought-sensitive cultivars under the −40 kPa treatment. Drought-resistant cultivars showed stronger resistance to drought in the −10 kPa treatment and obtained similar yield to the control, while the drought-sensitive cultivars were more obviously affected by the drought stress.
Highlights
Drought has become the main reason for crop yield reductions in the world
The peak of superoxide dismutase (SOD) activity of Songjing 6 (SJ6) treatments increased by 31.1%, 52.2%, 62.5%, respectively, while the SOD activity of DN25 treatments increased by 48.7%, 65.5%, 74.8%
The activity of catalase activity (CAT) in drought-sensitive cultivar SJ6 began to decrease before the return to irrigation under long-term drought at −40 kPa
Summary
Drought has become the main reason for crop yield reductions in the world. As a major food crop, rice is the most water intensive crop[1]. The overproduction of the plant leads to the excessive reduction of photosynthetic electron chains and the generation of reactive oxygen species under drought stress[8] These reactive oxygen species (ROS) such as superoxide anion (O⋅2−), hydrogen peroxide (H2O2), and hydroxyl radical (HO⋅), they are produced in different organelles and cause oxidative damage to cell components, lipid and protein peroxidation, DNA fragmentation, enzyme inhibition, and activation of programmed cell death pathways, may eventually lead to cell death[9,10]. Mehdy M C considered that drought stress on plant damage was a result of intracellular free radical production and the elimination of imbalance[11] It performed differently at different times under drought for rice. The drought stress and re-watering effects on the antioxidant system of two drought-tolerant rice varieties at the tillering stage were studied in order to clarify the changes in the antioxidant system of drought-resistant and drought-tolerant varieties under different drought stress in the tillering period and reveal the physiological mechanism of drought tolerance in rice for further study
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